1. Field of the Invention
The present invention relates to a fan apparatus, and specifically a small fan apparatus for blowing out heat which is generated inside a chassis of an electronic equipment.
2. Description of the Related Art
In an office automation (OA) equipment such as a personal computer or a copier, many electronic parts are housed in a chassis with a relatively small width. In such an OA equipment, heat generated from the above electronic parts stays in the chassis, thus possibly resulting in destroying the electronic parts. To prevent the problem, a vent hole is provided on the side wall or ceiling of the chassis and a fan is provided at the vent hole so as to blow out the heat generated in the chassis. Recently, in order to produce a large volume of air flow, a fan apparatus of series arrangement is used which is structured such that two axial-flow fans identical in outer shape and characteristics to each other are arranged axially in series (refer, for example, to Japanese Patent Application Laid-Open No. 2004-36569).
In order to securely provide a large volume of air flow while intending to downsize the fan apparatus, the motor of the axial-flow fan must be rotated in a high speed. To rotate the motor of the axial-flow fan in a high speed, a large current must be applied to the coil of the motor. Consequently, the coil increases its heat production resulting in increasing the amount of heat dissipated from the motor itself. At the same time, the amount of heat dissipated from the electronic parts is caused to increase which are mounted on the circuit board for driving the motor, and if the heat dissipated exceeds the operating temperature limit of the electronic parts, then the electronic parts may malfunction.
Under the circumstances described above, an axial-flow fan is proposed which blows out the heat generated by a motor rotating in a high speed (refer, for example, to Japanese Patent Application Laid-Open No. 2006-322451).
The fan apparatus of series arrangement disclosed in Japanese Patent Application Laid-Open No. 2004-36569 in which two axial-flow fans are arranged axially in series can securely provide a larger volume of air flow than a fan apparatus composed of one axial-flow fan, but two motors must be driven thus inevitably consuming more electricity. This does not comply with the demand for energy saving.
Also, in the axial-flow fan disclosed in Japanese Patent Application Laid-Open No. 2006-322451 in which a circuit board is attached on a plate which is fixed to the bottom surface of the case of a motor, the motor of the axial-flow fan must be downsized in accordance with downsizing of the fan apparatus. Consequently, the circuit board also must be downsized in accordance with reduction of the outer dimension of the motor of the axial-flow fan, but there exists a limitation due to a mounting layout of the electronic parts and therefore the circuit board cannot be downsized.